1. Field of the Invention
The present invention relates to a bellows structure which is blow-molded from a parison of a thermoplastic elastomeric material in a mold cavity defined in a mold including at least two mold parts which are separable apart when parisons are placed in the mold.
2. Description of the Prior Art
Bellows elements have conventionally been used as actuators for devices such as a damper disposed in an air induction system of an automotive internal combustion engine. Each bellows has an accordion-type convolution section and is blow-molded from a parison of a thermoplastic elastomeric material. The opposite ends of the accordion-type convolution section are closed by end sections having axial protrusions integrally formed on and axially outwardly extending from the central areas of the end sections so as to be engaged with mechanical elements to be drivingly connected to the bellows member. The axial protrusions are connected to the opposite ends of the accordion-type end section by generally annular shoulder portions each having an outer surface which extends smoothly and continuously in the circumferential direction of the bellows. Due to this design of each annular shoulder portion of the prior art bellows member, there has been a problem which will be discussed in detail with reference to FIGS. 1 to 6 of the accompanying drawings.